The introduction of frame relay in the early 1990's brought lower cost, higher bandwidth, improved reliability, and simpler management control to enterprise wide area networks (WANs) as compared to X.25 and point-to-point leased-line alternatives. Frame relay, together with single-source asynchronous transfer mode (ATM) and multiprotocol label switching (MPLS) services, still dominate the enterprise WAN market for corporate Internet traffic. A customer installs one of these networks and pays a single carrier a fee associated with the reliability and bandwidth the particular network provides. For example, a network may be advertised to provide “3 and ½ nines” (99.95%) or better reliability and have a fee based on this reliability and a cost per mega-bytes-per-second (Mbps). The present cost for such a network is almost as high as the fee paid back in 1998.
Applications such as Voice over IP (VoIP) have also become more pervasive and demand higher levels of Quality of Service (QoS) when run over the Internet. The quality of a call as well as reliability of the call duration have a clear expectation from the end users. While the deployment of VoIP over the Internet for making calls is new, the application of making a phone call over the Public Switched Telephone Network (PSTN) is not and users can easily detect poor call quality and a dropped call.
While performance, reliability, and predictability of a network have improved due to improvements in processor and communication architectures and implementations, these characteristics of a single network purchased from a single network provider are considered relatively low in performance, quality and are costly. Also, load balancing is still a difficult process due to the dynamic nature of networks.